Bicycle riding or cycling has remained a popular sport and recreational activity for many years. Bicycling has been known by several names including cycling or biking. Understandably, participants in this sport and recreation activity are found bicycling in a variety of environmental circumstances ranging from high speed competition racing to slow casual pleasure riding. One of the more interesting types of cycling to emerge through the years is that generally referred to as off-road biking or mountain biking. In this sport activity, participants often ride over extremely rough terrain and challenging hill and mountain trails subjecting the bicycle to extreme loading impact and stress.
To meet the need for using bicycles in this combination of high stress use and challenging terrain, practitioners in the art have endeavored to provide bicycles which are extremely strong and durable while remaining substantially lightweight to reduce the energy required to pedal such bicycles across the often hilly and challenging terrain. Thus, a typical off-road bicycle utilizes a lightweight frame having many parts fabricated from aluminum and magnesium alloys. To provide the impact or shock absorption characteristic required to assure the durability and strength of the bicycle, the typical off-road bike utilizes a frame fabricated of a plurality of frame portions coupled together to form spring controlled shock absorbing suspension components. The intent is that the multiply articulated shock absorbing frame be capable of sustaining substantial impact while relying upon the suspension system to absorb much of the energy and thereby avoid frame damage.
The drive system most typically used in such off-road bicycles generally comprises a plurality of sprockets grouped at the pedal crank and rear wheel and having a flexible chain coupled therebetween. A variety of gear ratios or drive ratios are provided through the use of a chain derailleur mechanism which operates to switch the coupling chain between various combinations of front and rear sprockets.
While the multiple sprocket chain drive systems in use are extremely effective and provide a wide range of drive ratios to aid the cyclist in traversing challenging hills and trails, a problem often arises due to the combined effect of the flexing shock absorbing frame and the chain drive system. This problem is known generally as "chain whipping" and arises as the articulated frame portions flex to absorb impact and as the loading upon the drive chain is varied in different circumstances to create undesired slack within the drive chain causing the drive chain to flip from or disengage the front sprocket. This problem can be extremely annoying to cyclists in that it requires stopping and resetting the chain upon the sprockets before continuing to ride. In addition, the sudden release of resisting load caused by the chain skipping from the drive sprocket also raises the possibility of injury to the rider.
Thus, there remains a continuing need in the art for evermore improved chain drive systems for bicycles. In particular, there remains a continuing need in the art for systems and apparatus which will minimize or prevent the occurrence of chain whipping in such bicycles.